Two unusual synapses in the mammalian cochlear nucleus which share a common input provide an opportunity not only to learn in detail how signals are transmitted and how auditory information is processed at a cellular level but also to study what mechanisms are involved in the development and maintenance of these synapses. Both bushy cells and octopus cells receive their input primarily from auditory nerve fibers through synapses on their cell bodies or on their short dendrites. Bushy cells are contacted by the ascending branch of VIII nerve fibers through end bulbs, or calyces, of Held. Octopus cells are contacted by the descending branch of VIII nerve fibers with two ultrastructurally distinct types of synaptic boutons. The fact that these cells have only short, stout dendrites makes them well suited for studies of synaptic mechanisms using intracellular recording techniques because microelectrodes in the cell bodies will necessarily be close to postsynaptic sites. To overcome the technical problems of recording intracellularly from an intact animal and to be able to control the extracellular environment, I propose to develop a brain slice preparation of the cochlear nucleus of mice. After learning to recognize bushy cells and octopus cells by their responses to electrical stimulation of the auditory nerve and to intracellularly injected current, I will be able to search for them and to focus on their physiology. Reversal potentials of postsynaptic potentials will be measured in a variety of ionic environments to identify the ion currents which underlie the postsynaptic potential changes. Pharmacological experiments will give an indication of what the chemical transmitters might be at these synapses. Perhaps it will be possible to measure miniature synaptic potentials and to do a quantal analysis of synaptic transmission. Are the functions of these three types of auditory nerve endings similar or different? Eventually I would like also to study the development of these synapses in the young animal by investigating their function in progressively younger animals. Some insight into the mechanisms that control the formation and maintenance of these particular synaptic contacts might also be gained from a study of mice with mutations that affect their auditory system.